As jellyfish population becomes a worldwide menace, how we treat our oceans needs urgent change

Jellyfish wreak havoc on the entire food chain. Without a curb on their population, growing hordes of jellyfish start eating the eggs of smaller fish, as well as their food supply.

Maneka Gandhi October 30, 2018 18:04:28 IST
As jellyfish population becomes a worldwide menace, how we treat our oceans needs urgent change

I just spent a week in monsoon-washed Goa — without going to the beach. The reason for this sacrilege? Jellyfish.

The Goa government has issued a warning to beach-goers that the state's beaches and coastal waters have swarms of live and dead jellyfish.

These long-tentacled gelatinous marine creatures are beautiful and deadly. The over 1,200 known varieties of jellyfish range from ones tiny enough to be ingested while swimming to as big as 200 kilogrammes.

As jellyfish population becomes a worldwide menace how we treat our oceans needs urgent change


The blue bottle and Portuguese man-of-war jellyfish currently invading Indian coasts have nematocysts on their tentacles, which can be as as long as 10 feet. These microscopic, barbed stinging structures can pierce human flesh and inject venom. People face the risk from dead jellyfish washed ashore, as well, as nematocysts remain potent in moist conditions for months.

The victim may experience skin irritation, muscle cramps, headache, nausea, diarrhoea and fever, and in extreme cases, acute pain, breathing difficulty, heart attacks and even death. One is more likely to die from a jellyfish sting than a shark attack.

As the population of jellyfish spins out of control, beaches have become dangerous for humans. Every year, thousands of people are stung. This was a major problem in the beaches of Mumbai, Goa, Kerala, Tamil Nadu and Andhra Pradesh in the monsoon this year. Now, there are jellyfish invasions throughout the year, with a bloom of jellyfish reported off the coast of Visakhapatnam for the first time.

Australia and Southeast Asia have the dreaded box jellyfish, whose venom causes the heart to seize. In the Philippines, 20 to 40 people die annually from box jellyfish stings.

The Irukandji is the size of a sugar cube, and its stinger leaves no trace. Ten minutes after contact, victims suffer excruciating lower back pain, incessant vomiting, constricted airways, brain clots and heart failure. "It's difficult to know how many victims the Irukandji have claimed," writes biologist Tim Flannery. "Many deaths have been attributed to stroke, heart attack or drowning."

Some 1,50,000 people are now treated for jellyfish stings in the Mediterranean each summer.

Jellyfish don't just sting' they have a huge economic and ecological impact. They are wreaking havoc the world over by disrupting food chains, causing massive power plant outages and jeopardising fisheries and tourism potential.

Jellyfish eat plant plankton and ichthyoplankton — the eggs and larvae of fish — as well as young fish, reducing fish populations. They can eat 10 times their body weight daily.

In the 1980s, a severe outbreak of comb jellyfish, brought from America in the ballast waters of foreign ships in the Black Sea, eliminated mackerel and anchovy fish and collapsed the $350 million Black Sea fishing industry. The jellyfish preyed on anchovy fish eggs and larvae and consumed the same zooplankton that the anchovies ate. Soon, the anchovy fishery industry crashed, and jellyfish bloomed. By 1993, it was 95 percent of the total biomass of the Black Sea.

Jellyfish now swarm all over. Fishermen nets in India are clogged with jellyfish. Estuaries in Kerala are often choked with heavy swarms. Fishing vessels that operate near shore waters net huge quantities.

Nuclear and thermal power plants use coastal waters for cooling, and discharge the heated water back into the seas. This increases temperatures by 1 to 1.5 degrees Celsius and affects waters for hundreds of miles. Jellyfish numbers increase in heated waters.

The atomic power station at Kalpakkam in Tamil Nadu suffered reduced production efficiency due to swarms of jellyfish clogging the sea water intake piping. On occasion, the plant has even been forced to stop production entirely.

Throngs of jellyfish have disrupted power generation everywhere from Muscat to Maryland, from South Korea to Scotland. Similar stories have been reported from power plants in the US, Sweden, China and Japan, where clogging has caused emergency situations at nuclear power plants and resulted in major power cuts and economic damage to cities. Nuclear plants in Japan are regularly shut down by jellyfish. In 1999, half of the Philippines lost power. The Persian Gulf systems of desalination, power plants and liquid natural gas plants have been affected by blooms since 2000.

Jellyfish have been around for centuries. Why are we facing overpopulation now?

It is entirely our fault.

The human race has created conditions that have led to an explosion of jellyfish blooms around the world.

Waste from farms and human settlements are thrown into waters that lead to the ocean. This leads to “eutrophication” (from the Greek eutrophos, meaning well-nourished). Nitrates and phosphates from sewage and fertilizers cause plants like algae and phytoplankton to flourish to such an extent that the whole surface of the dam/river/ocean is covered. This thick green surface algae blocks sunlight from reaching aquatic plants and marine creatures, killing them. Oxygen levels drop as the algae take oxygen from the water, causing the death of fish and molluscs. The water is acidified. Jellyfish thrive in this environment.

While killing larger fish, eutrophication supports the survival of plankton, larval sardines and other organisms that jellyfish feed on. The increase in jellyfish population has been found to match the increase in the occurrence of algal blooms in coastal waters. Eutrophication reduces water clarity and light penetration, which benefits jellyfish. Fish are visual feeders, while jellyfish are non-visual; turbid water reduces feeding by fish, but doesn’t affect jellyfish. Jellyfish need very little oxygen to survive. So as other animals dwindle, jellyfish colonies expand.

Moreover, over-fishing by humans has reached catastrophic levels and has led to a situation where most of the natural predators of jellyfish, such as sea turtles, salmon, mackerel, blue fin tuna, pilot whale and albatross, have become scarce. Jellyfish are eaten by 120 species of fish and 30 marine animals, including mushroom corals . Unfortunately, these fish are commercially fished. Their competitors for plankton and small fish, such as billfish and dolphins, are also endangered. Sea turtles, particularly leatherbacks and loggerheads, are suffocating on plastic in the ocean.

So jellyfish get a free run of the ocean and its small fish and larvae.Over-fishing has also made enormous room for plankton to grow.

Fish like anchovies, sardines and menhaden, which are plankton eaters, are harvested for fish meal for aquaculture. Plankton is the jellyfish's favourite food, and now, they have no competitor. By devouring huge quantities of plankton, jellyfish also deprive small fish species of food, and they stop breeding. A particularly large Nomura's jellyfish takes in enough seawater each day to fill a swimming pool, gobbling up any plankton it catches in the process.

Jellyfish wreak havoc on the entire food chain. Without a curb on their population, growing hordes of jellyfish start eating the eggs of smaller fish, as well as their food supply. They then occupy the niche that was once filled by other species. In Namibia, catches of anchovy and sardines have reduced dramatically since 1988, and large populations of two forms of jellyfish now predominate.

Aquaculture is increasing the number of jellyfish. The captive fish are free food; from giant shrimps, killed in India’s captive breeding stations, to salmon and trout in Scotland, Ireland and Norway. When additional feed is provided, eutrophication of the waters takes place. Aquaculture structures, like rafts, provide shade for polyps to grow.

Studies show that jellyfish started increasing in the 1980s, but have increased far more dramatically in the last 10 years.

Human structures built in the oceans have provided jellyfish with ideal places to reproduce. Jellyfish polyps need a solid structure to stick to to multiply, develop and 'hatch'. They have a variety of options to choose from — embankments, granite seawalls, docks, artificial reefs, floating plastic waste, ships and even offshore oil rigs. Even packets of cigarettes, plates and statues of religious idols serve as breading grounds for polyps to stick and grow.

Jellyfish thrive on ecosystems in distress. Biologist Lisa-Ann Gershwin writes: "As seas become stressed, the jellyfish are there, like an eagle to an injured lamb — more than just as symptom of weakness, more like the angel of death."


As jellyfish population becomes a worldwide menace how we treat our oceans needs urgent change

File photo of jellyfish. Image courtesy: Pixabay/Creative Commons

We need to urgently change the way we treat our oceans and the beings in it.

First, eutrophication needs to be controlled by reducing the nutrients that we indiscriminately empty into the oceans. Waste needs to go through much more stringent treatment before being let out into the sea.

We need to immediately stop overfishing. The huge trawlers, which amass tonnes of fish in one catch and throw away 90 percent of them as waste, need to be stopped completely. The government should introduce quotes to control the amount of fishing. This will increase the number of predators that feed on jellyfish.

Our permanent interventions in the sea, such as ports, marinas, offshore rigs, etc, need to be cleaned regularly so jellyfish polyps cannot survive on them. In fact, this practice of building structures in the ocean itself should be discouraged.

I know these solutions seem long term, but unfortunately, they are the only ones available. In any case, it may be too late, and we can’t do much to stop jellyfish from taking over the oceans.

From an evolutionary standpoint, jellyfish are biologically primed to take over the sea. They reproduce on the sea floor, or any other hard surface, and breed in massive numbers (in thousands per day). These blooms are increasing in intensity, frequency, or duration, says Lucas Brotz, a jellyfish expert at the University of British Columbia. Brotz’s research of 45 marine ecosystems shows an increase of 62 percent in blooms since 1950.

Will the oceans of the future soon be filled with jellyfish? They are moving closer to becoming the dominant species in the seas, filling the niche of the disappearing fish.

Global temperatures are expected to rise 0.2 degrees Celsius in the next two decades. The warming of the oceans will increase jellyfish populations. As the climate changes, the ocean currents change and blooms will crop up in new locations.

The current world human population is projected to increase 46 percent by 2050. Human influences and demands from the ocean will increase. Raised demands for energy will drive more dam and power plant construction, causing more sea warming in coastal waters.

For example, China has three operative nuclear power stations and four are under construction. Increased fertiliser use, particularly in Asia, will cause eutrophication to double. Global aquaculture has doubled between 1997 and 2020, with especially large increases occurring in developing nations. More fishing, more coastal development, and therefore, more opportunities for jellyfish, who are skilled at surviving in warm, polluted and acidified waters.

Our oceans' ecosystem is almost at its end. A new ecological system is coming along, with jellyfish at the top of the food chain. Once this stabilises, the removal of its dominance may prove difficult. Fish will almost disappear — even if we stop fishing. Jellyfish will also prevent the recovery of over-fished populations by eating their larvae.

Once jellyfish own the ocean, global warming will be even faster. Jellyfish promote climate change by releasing carbon-rich mucus and faecal matter. Marine bacteria uses this jellyfish to breed, which creates even more carbon dioxide and methane. "Climate change promotes jellyfish blooms, and jellyfish blooms promote climate change," said Gershwin, the author of Stung. "And like all robust feedback loops, where it stops, nobody knows."

You will soon be eating jellyfish curry instead of fish. Scientists from eight countries have begun a project called GoJelly to create jellyfish-based products — water filters, fish feed, face cream, fertilizers, food, salt , alcohol and jellyfish ethanol for cars.

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